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Roger Weller, geology instructor

by Haali Hale
Physical Geology
Fall 2010


Mica-The Mineral of Many Uses


What is Mica?

Mica, known to some as the invaluable mineral, is made up of aluminum silicate and alkalis with hydroxyl. Some forms of mica also contain lithium, iron, magnesium, and very rarely does mica contain manganese, vanadium, barium, and fluorine.  Mica has many different names including: Cat-Gold, Glist, Rhomboidal Mica, Cat-Silver, Katzengold, and Glimmer.  However, Mica is more commonly known as Muscovite.  Mica has basal (one-directional), perfect cleavage and splits into thin paper-like layers when broken in the direction of its cleavage.  While Mica is very brittle, it has useful thermal, chemical, and physical properties.



Why is Mica used in commercial industry?

                Mica is a large part of the electrical industry, mostly due to its vast dielectric strength.  Mica is also useful to the electrical industry due to its low level power loss and dielectric constant (the capacity for momentarily storing electrostatic energy).  Mica can withstand immense voltage while creating a safe pathway for the electricity to travel to and from its appointed destination.  Only two forms of mica, muscovite and phlogopite, are valued by the commercial industries because of their ability to tolerate the higher temperatures. Muscovite, however, is inferior to phlogopite; with phlogopite able to stand up to temperatures near one thousand degrees Celsius (muscovite can only stand temperatures near seven hundred degrees Celsius). 



What are the properties of Mica?

                Mica is a shiny, flaky substance that can be broken easily.  It also has perfect basal or one-directional cleavage and peels off in extremely thin layers.  Mica is a mineral that comes from a group of silicate minerals known as the mica group.  In addition, Mica is flexible, absorbs water easily (otherwise known as hydrophilic), is dielectric (a non-conductor of electricity), reflective, platy, and insulating.  Not only does Mica possess these characteristics, the color and transparency of this mineral vary greatly.  Micas can range in color from completely transparent (clear) to a slight opaque (milky but still can be seen through) all the way to a completely opaque substance (cannot be seen through at all).  Color is another important property of Mica, because of how many colors there are. There are green micas, red micas, black micas, clear or transparent micas, pearlescent micas, and many others.



Where is Mica found?

                Mica is found first and foremost in pegmatites, in a book-like formation.  Mica has gotten the reputation of looking like a book because of how much it peels.  Pegmatites are very coarse grained igneous rocks that have a grain size of about twenty millimeters or more.  These “hosts” of Micas are often a pale color, ranging anywhere from a light grey to a pink.  Sometimes, however, the pegmatite turns out to be a little more colorful, containing pink, grey, white, and black all in the same rock.
          Mica was found in great supply in Africa and South America during the nineteenth century, but is more commonly found in the Southwestern portion of the United States today, with India leading the world in Mica output. Many small Mica flakes will reflect off of each other in the mountainous terrain surrounding Southern Arizona, as well as New Mexico and California. Large concentrations of Mica can also be found in China, South Korea, Tanzania, Brazil, and the Malagasy Republic.


What are the different types of Mica?

                Although there are MANY types of Mica, over twenty in fact, the two main types of mica that are used are Muscovite Mica and Phlogopite Mica. There are also Lepidolite Micas, Paragonite Micas, Zinnwaldite Micas, and Biotite Micas.  Lepidolite Micas contain large amounts of lithium, Paragonite contains large amounts of sodium, Biotite with its large supply of magnesium and iron, and Zinnwaldite contains fair amounts of iron and lithium.

What are the uses of Mica?

                Although Muscovite and Phlogopite are more widely used than any other types of Mica, Lepidolite also has an important purpose. Lepidolite is used only to extract lithium. Lepidolite is the only source for lithium, which we use in batteries, and will soon be gone for good if we keep taking it out of our natural resources. Muscovite, the most commonly known form of mica, is the strongest and most durable form of mica as well. It is stronger and more insulating than any other form, as well as more resistant to moisture, more resilient, more transparent, and has more dielectric strength; this makes Muscovite the most significant mineral to the electrical industry. Mica is a thermal heaven for the electrical industry as well, able to withstand some of the highest temperatures used for electrical work. Mica is also very tough. It is not extremely durable when it comes to breaking it, but it can be punched out using a die cut, cut into smaller pieces, and it can also be machined.

                When used in its sheet form, Mica’s most natural form, it is used for an extremely wide variety of things.  Some of these uses for Mica include lighting, radar detectors, televisions, radios, generators, lasers, industrial strength electrical needs, optical filters, and so much more! Mica isn’t always in its solid form either. Sometimes, it is ground up into a fine powder to be used for things such as filling in the gaps in drywall, a substance known to some as joint compound. Paint extender is another use for ground mica powder as well, helping to prevent such great “wear and tear” due to weathering and it helps to cut down quite a bit on chalking.  It can be used for insulation, to keep sound from traveling, because of how lightweight it is. Another use for dry powdered mica is automobile manufacturing. Fenders and other car parts are often composed of materials that they combine with mica powder, since mica is so durable and resilient. Wet mica powder is used too, in rubber, wallpaper coatings, cosmetics, lubricants, and plastic. Wet mica powder is much more costly than the dry ground mica powder.



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